The present invention relates to a radio device comprising a receiving part formed by at least:
a selective high-frequency amplifier stage including a selective circuit that can be tuned to a certain tuning frequency.
The invention also relates to a method of adjusting one of the high-frequency amplifier stages included in such a device.
Such devices are well known and find many applications, notably in the field of portable telephones. It is necessary for this type of device to have a sensitive receiver that increases its range. The use of a selective amplifier improves the sensitivity.
A problem posed with such devices is the tuning of this selective amplifier. During manufacture, components are used whose values feature certain dispersion. One is thus confronted with the fact that the tuning frequency of the selective amplifiers varies from one specimen to the other at the end of the manufacture and also varies in dependence on temperature. To compensate this, habitually an adjusting capacitor is provided and its value is influenced so that the selective circuit is well tuned to the frequency band in which it is to operate. A temperature compensation is described in Japanese patent specification no. 07022974 of 24.01.1995. This compensation acts on a variable capacitance diode that also tunes the oscillation circuit, so that the total variation that can be applied to this diode is burdened with this compensation.
The present invention proposes a device of the type defined in the opening paragraph in which means are provided for facilitating the tuning of the selective stage without using notably the temperature meter and means for maintaining the voltage dynamic that can be applied to the tuning voltage if the selective circuit requires a certain dynamic in the tuning of its selective circuit. Therefore, such a device is characterized in that it comprises:
a received level meter for measuring the received level of the signals transmitted by a reference oscillator,
a variation element for causing the tunable band-pass circuit to vary as a function of a control magnitude,
a storage element for storing the control magnitude that gives the best level obtained by the level meter.
One of the ideas of the invention is to insert into the selective circuit one or various reactive elements that enable to center this selective circuit on the frequency range in which the device is supposed to operate.
These and other aspects of the invention are apparent from and will be elucidated, by way of non-limitative example, with reference to the embodiments described hereinafter.